Unidentified hackers have been attacking users of South Korea's two major portals in recent months to get their passwords and other personal information, an industry source said Wednesday.

The hackers are using phishing emails that entice users to click on a link to bring them to a fraudulent website, EST Security Corp., a cyber security firm, said.

The hackers named "Daum Post" sent phishing emails to some users of Daum, South Korea's No. 2 portal, saying their Daum accounts will be closed unless they click on a link that says "Upgrade Account Now," an official of EST Security said.

Once they click on the link, they are taken to a fraudulent site where they are required to provide ID and passwords.

Similar emails were also found by some users of Naver, the country's top portal operator, last month.

EST Security advised portal users to refrain from opening dubious emails and attached files and to frequently change their passwords. (Yonhap)